Cell structure
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Transcript of Cell structure
CELL STRUCTURE
Presented by Sneha Adhikari
Discovery of
cell
He invented microscope•With he could examine the specimens at magnification 1000-2000 times their original size
He studied cork slice under the microscope
He established that plant composed of cell
He established that animal composed of cell
Structures in a general plant cell
Structures in a general animal cell
Three imp cell regions
Cell membrane:- Outer most boundary of cell
Nucleus:- Control centre of the cell that contains DNA
Cytoplasm:- Part between the nucleus & cell membrane.
It contains a liquid called as cytosol which may contains cell organelles.
Cell wall STRUCTURE PLANT
Only plant cells andbacterial cells possesa protective structureas the cell wall outside the plasma membrane.In bacteria It is basically made up of long
polymers of glucosamine (NAG) and muramic acids (NAM)
In higher plants cell walls mainly made up of cellulose fibres. Addition to these, pectins, hemicelluloses and lignin are also deposited on primary cellulose layer.
Cell wall made up of three layers1.Middle lamella: it is composed of pectates of Ca &Mg.2.Primary cell wall: It is the first true cell wall to be deposited & made up of Cellulose, hemicellulose & some polysaccharides. 3.Secondary cell wall: it is made up of cellulose,hemicellulose and other polysaccharides impregnated with lignin, suberin,Si,Ca,Mg.
Cell wall functions
It a rigid, dead & protective covering.
Cell membrane structure
Cell membrane It is also known as plasma membrane.It is composed of two layer of phospholipids.A phospholipid is a type of fat composed of1. A hydrophilic phosphate head that faces aqueous environment. 2.Two hydrophobic fatty acid tails that faces
other fatty acid tail.
Cell membranes may also contain protein, sterols & sugarFor the structural organization of various compounds with in the membrane various theories were given:1. Trilamellar model or Sandwich model: By
Denielli Davson2. Unit membrane model : By Robertson3. Fluid mosaic model : By Singer & Nicolson proteins & lipids are oriented towards each
other in such a way, they exhibit semi fluid properties & the arrangement of lipids and proteins is of mosaic pattern
Cell membrane function
1.Responsible for protecting and separating the protoplasm from the external environment
2.Helps in selective uptake and transport Of ions
3.Provides surface area for many biochemical signal transduction reaction.
4. Plasma membrane is also the site for pinocytosis and phagocytosis.
Nucleus structure
It also known as master organelle.In some cases like sieve tubes, in plants
and red blood cells in animals nucleus disappears at the later stages of development.
Nucleus FUNCTIONS
Nucleolus is very important structure for; it acts as the site of synthesis and assembly of cytoplasmic ribosome's.
Karyolyph contains all the required components for the DNA replication and repair, transcription, assembly of ribosome's.
It play imp role in inheritance & gene expression
Mitochondria structure
Mitochondria are considered as ‘power plants’ of the cells. Whenever or wherever, there is a need for higher amount
of energy output, mitochondria are found in large number.Mitochondria absent in RBC of mammals.Mitochondria are bounded by two single unit membranes.
Mitochondria Functions
Also known as power house of the cell.Krebs cycle accur in matrix of
mitochondria.Enzymes responsible for ETS located in
inner membrane.
Endoplasmic reticulum structureIt is in contact with the outer plasma lemma and
the outer nuclear membrane.Absent in mature erythrocytes and cells of bacteria.ER is made up of two single unit membranes.Ultra structures: 1.Cisternae 2.Tubules
Endoplasmic reticulum functions
Mechanical support for the fluid protoplasm
Synthesis and storage of lipidsSynthesis and storage and transport
of proteins to different destination through golgi membranes.
Detoxification, transport of various cellular components, formation of micro bodies, formation of secretory vesicles
Golgi body StructureGolgi complex is surrounded by Endoplasmic reticulumThey are present in all cells except bacterial and blue-
green algal cells. In secretory tissues like thyroid and liver they are present
in large numbers than in other type of cells.The stacked Golgi membranes have two faces, i.e.
formation face is called cis face and maturation face as trans face.
Golgi body functions
Glocolysation of proteins Synthesis of cell wall
polysaccharidesMaturation of zymogen granules Formation of primary lysosomesSecretion of lipid bodiesPacking, maturation and
secretion of specific substances are the most important events of Golgi functions
Plastid Structure Plastids are very important cell organelles found mostly in
plant cells. They are mainly responsible for photosynthesis. plastids have been broadly classified into colorless plastids
(Leucoplasts) and color plastids (Chromoplasts). CHLOROPLAST: Basically most of the chloroplasts are bounded by two single
unit membranes and the space between them is called periplastid space
Plastids Functions
Chloroplasts perform light reactions where light energy captured, converted into chemical energy and stored in energy rich bonds of ATP and reducing power NADPH+H.
Ribosome Structure Ribosomes are ultramicroscopic particles, first observed by Palade They have been broadly classified into two types, i.e. 80 S and 70 S
types. Ribosomes found in the cytoplasm exist either in membrane bound
state or free state. It is made up of 2 sub units 1. larger (Dome) 2.smaller(cup
shaped) These two units united with the help of Mg+2
Ribosome's functionsRibosome act as dynamic
machinery for the synthesis of proteins. This is achieved by the association of ribosome's with messenger RNA (m.RNA) and amino acid loaded transfer RNA
Lysosomes StructuresAlso known as suicidal bags.Lysosomes are bounded by a single
unit membrane and enclose a group of hydrolytic enzymes.
Lysosomes are divided in 4 parts 1. primary lysosomes 2. secondary lysosomes/ digestive
vacuoles 3.Residual bodies 4.Autophagic vacuoles
Lysosomes Functions It helps in 1.Phagocytosis 2.AutophagyPlay a very important role in metamorphosis of amphibians
and insects. For example, during the transformation of tadpole into adult frog; the long tail of the tadpole gets digested by the lysosomal activity, the process called resorption
Micro bodies StructureThey are bounded by a single unit
membrane. Such structures are found in both animal and plant cells
There are three types of micro bodies and they are characterized by their functions:
1.Sphaerosomes 2.Peroxisomes 3.Glyoxysomes
Vacuoles Structure
Vacuoles are the spaces in the cells surrounded by single unit membranes.
It is separated from the rest of the cytoplasm by a single unit membrane called tonoplast.
It is filled with cell sap.
Vacuoles FunctionsThe content of the cell vacuole is
important in maintaining the turgidity of the cells.
These vacuoles have been found to show lysosomal activities.
Cytoskeleton Structure1. Micro tubules: fine tubuler proteins Functions: 1.provides structural support to various cell. 2.Help in spindle & astral ray formation
2. Micro filaments: thin protein fibreFunction:1.Amaeboid movement of protozoans
Centrioles StructureCentrioles are the characteristic organelles of animal cells
they are almost absent in plant cells with the exception of some lower unicellular algae.
They are found in the cytoplasm at one pole of the nucleus.The wall of the open barrel shaped structure is made up of
nine groups of microtubules arranged in a circle.
Centrioles FunctionsCilia and flagella in lower
organisms and other cells take their origin from centrioles
During cell division, centrioles help in the organization of mitotic apparatus in a particular plane.
Polymerise cell microtubules for formation of spindle fibres and astral rays during cell division
Chromosome StructureDarkly stained rod shaped bodies visible under light
microscope in cell during metaphase stage of mitosis.Chromosome morphology 1. Centromere 2. Cromatid 3. Secondary constriction
4. Telomere 5. Chromomere 6. Chromonema 7. Matrix
Chromosome Function
It carry DNA so it play role in inheritance.
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